<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<form action="user" method="get">
  请输入用户名:<input type="text" name="username" /> <br>
  <input type="submit" value="校验">
</form>
<br>
<form action="s3" method="get">
  get请输入用户名:<input type="text" name="username" /> <br>
  <input type="submit" value="校验">
</form>
<br>
<form action="s3" method="post">
  post请输入用户名:<input type="text" name="username" /> <br>
  <input type="submit" value="校验">
</form>
</body>